In ticket handling apparatus in which a value or other data must be printed on a ticket, the basic essential needs are means for feeding the ticket through, or into and out of the mechanism, and means for performing the printing operation. Some systems utilize a ticket which is purchased for an initial value, and the cost of services is deducted from that value at each use. When the value is constant, or one of a few selectable increments, the printer can be preset to update the ticket value in a simple manner.
When the value of service is variable, however, as for transportation between various points in a rapid transit system, the value must be determined at each use. In one type of system not in use, the ticket carries a magnetic stripe, on which pertinent data, such as ticket value, point of entry into the system and other such information, are recorded in coded form. At the point of exit, the ticket handling machine reads this information, the appropriate value of service is calculated and the magnetic record is suitably updated. For benefit of the ticket holder the updated value is also printed on the ticket. The system is, of course, controlled by and all calculations and data updating performed by a computer.
Since speed is of the essence in a rapid transit system, the printing must be accomplished in a very short time. Manual insertion and removal of a ticket is not desirable, because the speed of ticket motion is not constant, insertion may not be perfect and fumbling can prevent proper operation. It is thus preferably to feed a ticket through the mechanism automatically.
Printing mechanisms are a problem in a high speed automatic operation, since the required value must be set up in a fraction of a second and the printing accomplished either while the ticket is moving, or when the ticket is stopped. Printing on a moving ticket has obvious problems and usually involves a moving printer head and precise timing. Stopping the ticket at the precise position for successive line printing is also difficult and the results have been far from satisfactory.